This message should not appear if a regular CS2D client is used. So it's either a bad custom piece of software which is (maybe unintentionally) sending too many requests or it's an intended attack.

Basically impossible to tell if these errors were triggered by actual DDoS attacks. Seeing the console log alone is not sufficient to see that. You would have to see the overall incoming traffic at these times.

No, IPs of DDoSers are NOT shown in the console at any time. CS2D does not have any DDoS detection. The message you see there only tells you that someone with the specified IP sent the info requests suspiciously frequently.

This CAN be a sign for a DoS or a DDoS but it might also be something else.